(The restaurant I work in offers discount vouchers when customers subscribe in the website. In this case, the voucher was 2 courses for 10. After receiving her bill, a lady comes to me and starts arguing.)

Customer: “Why is my discount £3 when the voucher is for £10?”

Me: “Ma’am, the voucher does not give you £10 off your bill. It gives you the two courses for £10.”

Customer: “No, no! The voucher says £10!”

(After explaining the promotion for nearly 10 minutes, the manager joins in to help. Finally, the customer’s friend realizes the point of the promo and explains it.)